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Chapter 14 Some compounds with Oxygen, sulfur, or a Halogen: Alcohols, Phenols, Ethers, and Thiols Structure and Classification of Alcohols 14.3 Naming Alcohols, Phenols, and Thiols 14.4 Some Important Alcohols and Phenols Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 1 Alcohols In an alcohol, a hydroxyl group (—OH) is attached to a carbon chain. In a phenol, a hydroxyl group (—OH) is attached to a benzene ring. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 2 Classification of Alcohols Alcohols are classified as primary, secondary, or tertiary. Classification is determined by the number of alkyl groups attached to the carbon bonded to the hydroxyl. Primary (1º) 1 group H | CH3C—OH | H Secondary (2º) 2 groups CH3 | CH3—C—OH | H Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. Tertiary (3º) 3 groups CH3 | CH3—C—OH | CH3 3 Learning Check Classify each alcohol as 1) primary, 2) secondary, or 3) tertiary. OH | A. ___CH3—CH—CH2—CH3 B. ___ CH3—CH2—CH2—OH C. ____HO—CH2—CH2—CH2—CH2—CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4 Solution Classify each alcohol as 1) primary, 2) secondary, or 3) tertiary. OH | A. 2 CH3—CH—CH2—CH3 B. 1 CH3—CH2—CH2—OH C. 1 HO—CH2—CH2—CH2—CH2—CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 5 Naming Alcohols The IUPAC system replaces the -e in the name of the alkane main chain with –ol. Common names for simple alcohols use the alkyl name followed by alcohol. CH3OH CH4 methane methanol (methyl alcohol) CH3CH3ethane CH3CH2OH ethanol (ethyl alcohol) Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 6 Naming Alcohols In the IUPAC names for longer chains, the chain is numbered from the end nearest the -OH group. 1-propanol CH3—CH2—CH2—OH OH | CH3—CH—CH2—CH3 2-butanol CH3 OH | | CH3—CH—CH2—CH—CH3 4-methyl-2-pentanol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 7 Some Typical Alcohols OH | “rubbing alcohol” CH3—CH—CH3 2-propanol (isopropyl alcohol) antifreeze glycerol HO—CH2—CH2—OH 1,2-ethanediol (ethylene glycol) OH | HO—CH2—CH—CH2—OH 1,2,3-propanetriol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 8 Learning Check Name the following: A. CH3—CH2—CH2—CH2—OH B. OH CH3 | | CH3—CH—CH—CH2—CH3 OH C. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 9 Solution A. CH3—CH2—CH2—CH2—OH 1-butanol OH CH3 | | B. CH3—CH—CH—CH2—CH3 3-methyl-2-pentanol OH C. cyclopentanol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 10 Learning Check Write the structure of each of the following: A. 3-pentanol B. ethyl alcohol C. 3-methylcyclohexanol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 11 Solution Write the structure of the following: A. 3-pentanol OH | CH3—CH2—CH—CH2—CH3 B. ethyl alcohol CH3—CH2—OH OH C. 3-methylcyclohexanol CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 12 14.5 Reactions of Alcohols Alcohols undergo combustion with O2 to produce CO2 and H2O. 2CH3OH + 3O2 2CO2 + 4H2O + Heat Dehydration removes H- and -OH from adjacent carbon atoms by heating with an acid catalyst. H OH | | H+, heat H—C—C—H H—C=C—H + H2O | | | | H H H H alcohol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. alkene 13 Formation of Ethers Ethers form when dehydration takes place at low temperature. H+ CH3—OH + HO—CH3 CH3—O—CH3 + H2O Two Methanol Dimethyl ether Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 14 Oxidation and Reduction In organic chemistry, oxidation is a loss of hydrogen atoms or a gain of oxygen. In an oxidation, there is an increase in the number of C-O bonds. Reduction is a gain of hydrogen or a loss of oxygen. The number of C-O bonds decreases. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 15 Oxidation of Primary Alcohols In the oxidation [O] of a primary alcohol, one H is lost from the –OH and another H from the carbon bonded to the OH. [O] Primary alcohol OH | CH3—C—H | H Aldehyde [O] Ethanol (ethyl alcohol) Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. O || CH3—C—H + H2O Ethanal (acetaldehyde) 16 Oxidation of Secondary Alcohols The oxidation of a secondary alcohol removes one H from –OH and another H from the carbon bonded to the –OH. [O] Secondary alcohol OH | CH3—C—CH3 | H 2-Propanol (Isopropyl alcohol) Ketone O || CH3—C—CH3 + H2O [O] Propanone (Dimethylketone; Acetone) Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 17 Oxidation of Tertiary Alcohols Tertiary alcohols are resistant to oxidation. [O] Tertiary alcohols no reaction OH | [O] CH3—C—CH3 no product | CH3 no H on the C-OH to oxidize 2-Methyl-2-propanol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 18 Learning Check Select the product for the reaction of CH3—CH2—CH2—OH with the following reagents: A. B. C. H+, heat [O] O2, spark Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 19 Solution A. H+, heat 1) CH3—CH=CH2 O || B. [O] C. O2 3) CH3—CH2—C—H spark 2) CO2 + H2O Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 20 Ethanol CH3CH2OH Ethanol: Acts as a depressant. Kills or disables more people than any other drug. Is metabolized at a rate of 12-15 mg/dL per hour by a social drinker. Is metabolized at a rate of 30 mg/dL per hour by an alcoholic. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 21 Oxidation of Alcohol in the Body Enzymes in the liver oxidize ethanol. The aldehyde produced impairs coordination. A blood alcohol level over 0.4% can be fatal. O || CH3CH2OH CH3CH 2CO2 + H2O Ethyl alcohol acetaldehyde Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 22 Effect of Alcohol on the Body Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 23 Alcohol Contents in Common Products % Ethanol 50% 40% 15-25% 12% 3-9% Product Whiskey, rum, brandy Flavoring extracts Listerine, Nyquil, Scope Wine, Dristan, Cepacol Beer, Lavoris Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 24 14.6 Phenols A phenol is a benzene ring with a hydroxyl group. For two substituents, assign C-1 to the carbon attached to the –OH. Number the ring to give the lowest numbers. The prefixes o, m, and p are used for common names. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 25 Examples of Phenols OH OH OH Cl Br Phenol 3-Chlorophenol (m-Chlorophenol) Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4-Bromophenol (p-Bromophenol) 26 Phenols in Medicine Many phenols are used as antiseptics and disinfectants. OH OH OH OH OH CH2CH2CH2CH2CH2CH3 Phenol Resorcinol (antiseptic) Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 4-Hexylresorcinal (antiseptic) 27 Derivatives of Phenol Compounds of phenol are the active ingredients in the essential oils of cloves, vanilla, nutmeg, and mint. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 28 14.7 Acidity of Alcohols and Phenols Alcohols and phenols are weakly acidic. They dissociate slightly in aqueous solution and establish equilibria between neutral and anionic forms. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 29 Alcohols are about as acidic as water. Ka values near 10-15. Thus, an alkoxide ion (RO-) is as strong a base as hydroxide, HO-, ion. Phenols are considerably more acidic than water. Ka value 1.0 x 10-10. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 30 14.8 Ethers Ethers contain an -O- between two carbon groups. Simple ethers are named by listing the alkyl names in alphabetical order followed by ether. CH3—O—CH3 dimethyl ether ethyl methyl ether CH3—O—CH2—CH3 CH3—CH2—O—CH2—CH3 diethyl ether Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 31 An –OR group is known as an alkoxy group. -OCH3 is a methoxy, -OCH2CH3 is a ethoxy group, and so on. These names are used when the ether functional group is present in a compound that also has other functional groups. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 32 IUPAC Names for Ethers In the IUPAC system, the shorter alkyl group and the oxygen are named as an alkoxy group attached to the longer alkane. methoxy propane CH3—O—CH2—CH2—CH3 Numbering the longer alkane gives 1-methoxypropane. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 33 Learning Check Name each of the following compounds: A. CH3—CH2 —O—CH2—CH3 CH3 | B. CH3—CH2—CH—CH2—CH2—OH C. CH3—CH2—CH2—SH Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 34 Solution Name each of the following compounds: A. CH3—CH2 —O—CH2—CH3 Diethyl ether or ethoxyethane (IUPAC) CH3 | B. CH3—CH2—CH—CH2—CH2—OH 3-Methyl-1-pentanol C. CH3—CH2—CH2—SH 1-Propanethiol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 35 Learning Check Draw the structure of each compound. A. 2-Butanethiol B. Ethyl methyl ether C. 2-Methyl-1-butanol Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 36 Solution Draw the structure of each compound. A. 2-Butanethiol SH | CH3—CH—CH2—CH3 B. Ethyl methyl ether CH3—CH2—O—CH3 C. 2-Methyl-1-butanol CH3 | HO—CH2—CH—CH2—CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 37 Boiling Points of Alcohols Alcohols contain a strongly electronegative O in the OH groups. Thus, hydrogen bonds form between alcohol molecules. Hydrogen bonds contribute to higher boiling points for alcohols compared to alkanes and ethers of similar mass. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 38 Boiling Points of Ethers Ethers have an O atom, but there is no H attached. Thus, hydrogen bonds cannot form between ether molecules. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 39 Solubility of Alcohols and Ethers in Water Alcohols and ethers are more soluble in water than alkanes because the oxygen atom can hydrogen bond with water. Alcohols with 1-4 C atoms are soluble, but alcohols with 5 or more C atoms are not. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 40 14.9 Thiols Thiols are carbon compounds that contain the –SH group. In the IUPAC name, thiol is added to the alkane name of the longest carbon chain. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 41 Naming Thiols In thiols with long carbon chains, the chain is number to locate the -SH group. CH3—CH2—CH2—SH SH | CH3—CH—CH3 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 1-propanethiol 2-propanethiol 42 Thiols in Nature Thiols: Often have strong or disagreeable odors. Are used to detect gas leaks. Are found in onions, oysters, and garlic. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 43 14.10 Halogen Containing Compounds Akyl halide (RX): The simplest halogen containing compounds. In alkyl halides, an alkyl group is bonded to a halogen atom. The common names of alkyl halides are formed by giving the name of the alkyl group followed by the halogen name with an –ide ending. Examples, CH3Br – methyl bromide; CH3CH2I – Ethyl iodide Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 44 Systematic names are obtained by considering the halogen atom as a substituent on a parent alkane. The parent alkane is named by selecting the longest chain and numbering from the end nearer the first substituent, either halogen or alkyl. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 45 Halogenated organic compounds are used as Anesthesia. For example, halothane is an important anesthetic. Solvents insecticides Feed stock in chemical industries Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 46 Chapter Summary Alcohols has, R-OH, –OH group attached to a saturated alkane-like carbon atom. Phenols, Ph-OH, has –OH group attached to an aromatic ring. Thiols are sulfur analog of alcohols, R-SH. Alkyl halides contain a halogen atom bonded to an alkyl group. Alcohols are named using the –ol ending, and phenols are named using the phenol ending. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 47 Chapter Summary Contd. Ethers are named by identifying the two organic groups attached to oxygen, followed by the word ether. Thiols use the name ending –thiol. Alkyl halides are named as halogen substituted alkane. Alcohols and phenols are polar, they are capable of participating in hydrogen bonding. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 48 Chapter Summary Contd. Solubility of alcohols in water decreases as the size of the organic group increases. Ethers do not hydrogen bond, and more like alkane in their properties. Alcohols and phenols are weak acids. Alcohols are similar to water in acidity; phenols are more acidic than water. Alcohols undergo dehydration reaction (loss of water) to yield alkene when treated with a strong acid. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 49 Chapter Summary Contd. Alcohols undergo oxidation reaction to yield carbonyl (C=O) group containing product. Oxidation of primary alcohols produce either aldehyde (RCH=O) or carboxylic acid (RCO2H), depending on the reaction conditions. Oxidation of secondary alcohols produce ketones (RCH=O). Tertiary alcohols generally does not participate in oxidation reactions. Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 50 End of Chapter 14 Copyright © 2004 Pearson Education Inc., publishing as Benjamin Cummings. 51